The present invention relates to an optical barrier apparatus used in safety equipment and the like for industrial machinery. In particular the invention relates to an optical barrier apparatus (also referred to as an optical barrier sensor) for scanning a detection area with an optical beam, and judging the absence of object when a reflection beam of the optical beam is received, and judging the presence of object when not received.
As such an optical beam scanning type optical barrier apparatus, there is the apparatus disclosed for example in PCT International Publication No. WO97/33186, and this will be briefly described.
In FIG. 2 of PCT International Publication No. WO97/33186, a laser beam generating means and a laser scanning means are arranged on one side of a detection area, and an array light receiving elements is arranged on the other side. In this apparatus, a laser beam generated by the laser beam generating device is projected onto the laser scanning device, and the laser scanning device reflects the laser beam so as to scan an area including the detection area. If an object is not present inside the detection area, the laser beam is received by the light receiving element array. If an object is present inside the detection area, the laser beam is blocked by the object so that the light receiving element positioned in the shadow of the object within the light receiving element array does not receive the laser beam. The deficiency of light reception output signal from the light receiving element array, which occurs at this time, is detected by a signal deficiency detecting means, thus notifying of the presence of object.
Furthermore, in FIG. 3 and FIG. 6 of PCT International Publication No. WO97/33186, there is disclosed a construction which uses a reflecting mirror.
In FIG. 3, the construction is such that a laser beam generating device, a laser scanning device and a light receiving element array are arranged on the same side, and a concave reflecting mirror is arranged on the other side. A laser beam generated by the laser beam generating device is scanned at a predetermined spread angle by the laser scanning device, and projected onto the concave reflecting mirror arranged on the other side. The laser beams reflected by the concave reflecting mirror are passed through a detection area as mutually parallel beams to be directed towards the light receiving element array. Furthermore, in FIG. 6, the construction is such that the light receiving element array of FIG. 3 is replaced with a single light receiving element, and the position of the laser scanning device and the shape and position of the concave reflecting mirror are adjusted so that the reflected light of the concave reflecting mirror is focused onto the single light receiving element.
However, with the abovementioned optical beam scanning type optical barrier apparatus, in the constructions of FIG. 2 and FIG. 3, since a light receiving element array is used, it is necessary to adjust light reception directional characteristics of the light receiving element array with respect to each of the elements. Furthermore, a light receiving circuit is needed for each of the respective light receiving elements, and hence there is a problem in that cost reduction is difficult.
Furthermore, with the construction of FIG. 6, the light receiving element is only one, and hence the cost can be reduced compared to FIG. 2 and FIG. 3. However there is a problem in that there exists an area where the object detection is not possible, and the detection area thus becomes narrow.
The present invention addresses the abovementioned problems with the object of providing an optical barrier apparatus enabling of cost reduction without narrowing the detection area.
In order to achieve the aforementioned object, an optical barrier apparatus according to the present invention comprises a first and second units facing each other with a detection area therebetween, each of the first and second units comprising: optical beam generating means, optical beam scanning means for reflecting an optical beam generated by the optical beam generating means so as to scan an area containing the detection area, optical beam reflecting means for reflecting a scanning beam incident from the optical beam scanning means via the detection area by turning back at approximately 180 degrees, light receiving means arranged in the vicinity of the optical beam scanning means for receiving a reflection beam from the optical beam reflecting means, and signal deficiency detecting means for detecting the presence/absence of a deficiency of output signal of the light receiving means and generating a notification output for object absence at the time of no deficiency, wherein the optical beam scanning means and the light receiving means of the first unit and the optical beam scanning means and the light receiving means of the second unit are arranged on either side of the detection area at approximately diagonal positions.
With such a construction, the optical beam generated from the optical beam generating means is reflected and scanned by the optical beam scanning means. If an object is present in the detection area, the scanning beam does not reach the optical beam reflecting means so that an optical beam at a predetermined level or above is not received by the light receiving means. If an object is not present in the detection area, the scanning beam is reflected by the optical beam reflecting means and the light receiving means receives a reflection beam at a predetermined level or above. The signal deficiency detecting means, if an output level of the light receiving means is at the predetermined level or above, generates a notification output for object absence. This type of object detection is respectively performed in the first unit and second unit. Moreover, since the optical beam scanning means and light receiving means of the first unit, and the optical beam scanning means and light receiving means of the second unit are arranged at diagonal positions on either side of the detection area, the area where object detection is possible becomes a rectangular shape. As a result, the number of light receiving means can be reduced, costs can be reduced, and the detection area becomes rectangular so that the detection area can be widened.
The construction may be such that there is provided synchronous drive means for synchronizing the two optical beam scanning means of the first and second units with respect to each other so that when a scanning beam direction on the first unit side is a diagonal direction, a scanning beam direction on the second unit side is also a diagonal direction. Then, when a scanning beam direction of one unit is a diagonal direction where it is easy for an optical beam from the other unit to be erroneously received, if an object is present on an optical axis of an optical beam from the one unit, the scanning beam is blocked by the object so that erroneous notification attributable to reception of the scanning beam of the other unit can be prevented.
Moreover, the construction may be such that there is provided selection drive means for selectively driving the first and second units so that object detection operations of the first unit and second unit are not performed at the same time. Since when one unit is being driven the other unit is stopped, erroneous notification attributable to reception of the scanning beam of the other unit can be prevented.
Furthermore, the construction may be such the emission wavelengths of optical beams respectively generated from the respective optical beam generating means of the first unit and second unit are made different from each other. Moreover, the construction may be such that blinking frequencies of reflection beams respectively reflected from each optical beam reflecting means of the first unit and second unit are made different from each other. In this case also, since the optical beam of the own unit and the optical beam of the other unit can be distinguished, erroneous notification attributable to reception of the scanning beam of the other unit can be prevented.
Moreover, the construction may be such that each signal deficiency detecting means verifies that a light reception output from the light receiving means is one based on a reflection beam from the optical beam reflecting means, to generate a notification output for object absence.
With such a construction, since it becomes possible to distinguish between the reflection light from the optical beam reflecting means and the light reflected by the object, then even in the case where the reflectance of the object is high so that the light reception level of reflection light from the object is equal to or above a predetermined level, or the case where the object is near the light receiving means so that the light reception level of irregularly reflected light from the object is equal to or above a predetermined level, erroneous notification can be prevented.
Furthermore, the construction may be such that scanning verification means for verifying that the scanning beam is scanned within a range of the area including the detection area is provided in each unit.
With such a construction, it becomes possible to verify with the scanning verification means, that the scanning beam is normally scanning the detection area. Therefore, in the case where this construction is used as a safety ensuring facility for a machine, reliability for the optical barrier apparatus can be improved.